Electronic device with central and peripheral displays

ABSTRACT

An electronic device such as a head-mounted device may have a display that is viewable by a user from eye boxes. The electronic device may have a gaze tracking system that monitors a user&#39;s eyes in the eye boxes to gather gaze direction information. The display may have a central portion and a peripheral portion. The peripheral portion may have a lower resolution than the central portion and may be used in displaying content that is viewable in a user&#39;s peripheral vision. During operation, control circuitry in the electronic device may adjust peripheral content on the peripheral portion to correct for parallax-induced mismatch between the peripheral content and central content on the central portion of the display. The control circuitry may also depower peripheral pixels that are determined to be unviewable based on the gaze direction. Diffusers may be used to hide seams between the central and peripheral display portions.

This application claims the benefit of provisional patent applicationNo. 62/725,141, filed Aug. 30, 2018, which is hereby incorporated byreference herein in its entirety.

FIELD

This relates to electronic devices, and, more particularly, tohead-mounted devices.

BACKGROUND

Head-mounted devices such as virtual reality headsets can be used toprovide virtual reality content to a user. The virtual reality contentmay contain computer-generated content for games and other movingimages.

Challenges can arise in presenting virtual reality content to a user. Ifcare is not taken, the display structures that are used in presentingthe content will not cover the user's peripheral vision, which willdetract from the immersive nature of the user's virtual realityexperience.

SUMMARY

An electronic device such as a head-mounted device may have a display.The display may be coupled to head-mounted support structures. Lensesmay be aligned with eye boxes. When a user's eyes are located in the eyeboxes, content on a central portion of the display may be viewed throughthe lenses. Peripheral content on peripheral portions of the display maybe viewed from the eye boxes without the lenses. The peripheral portionmay have a lower resolution than the central portion and may be used indisplaying content that is viewable in a user's peripheral vision.

The electronic device may have a gaze tracking system that monitors auser's eyes in the eye boxes to gather information on the gaze directionof the user's eyes. During operation, control circuitry in theelectronic device may use the gaze direction information to adjustperipheral content on the peripheral portion to correct forparallax-induced mismatch between the peripheral content and centralcontent on the central portion of the display. The control circuitry mayalso depower peripheral pixels that are determined to be unviewablebased on the gaze direction information.

Diffuser structures may be used to help hide the boundary between thecentral and peripheral display portions. The diffuser structures may beformed from lens holder structures that support the lenses or a separatediffuser layer. A neutral density filter may be used to reduce pixelbrightness in the peripheral display portion. Pulse width modulationschemes may also be used to regulate pixel intensity.

The peripheral content may be derived from edge portions of the centralcontent or may be independently provided content. Peripheral pixels maybe formed on a flexible substrate or other mounting structure. In someconfigurations, the peripheral pixels may be formed on a surface with acurved profile such as a surface with compound curvature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illustrative head-mounted device inaccordance with an embodiment.

FIG. 2 is a top view of a portion of an illustrative head-mounted devicein accordance with an embodiment.

FIG. 3 is a cross-sectional side view of a portion of an illustrativeperipheral display in accordance with an embodiment.

FIG. 4 is a cross-sectional top view of a portion of an illustrativehead-mounted device in accordance with an embodiment.

FIG. 5 is a cross-sectional top view of a portion of an illustrativehead-mounted device having a light-diffusing lens holding structure inaccordance with an embodiment.

FIG. 6 is a cross-sectional top view of a portion of an illustrativehead-mounted device with a diffuser in accordance with an embodiment.

FIG. 7 is a side view of an illustrative eye showing different possiblegaze directions that may be measured with a gaze tracking system inaccordance with an embodiment.

FIG. 8 is a front view of an illustrative display showing how content onthe display may be susceptible to parallax effects depending on thedirection of gaze of a user in accordance with an embodiment.

FIG. 9 is a flow chart of illustrative operations involved incompensating for parallax in accordance with an embodiment.

FIG. 10 is a front view of an illustrative display showing regions withcontent that may be expanded over peripheral display portions to hideinterfaces between central and peripheral display portions in accordancewith an embodiment.

FIG. 11 is a top view of an illustrative display showing how pixels inthe display may be selectively depowered or otherwise adjusted based ongaze direction in accordance with an embodiment.

FIGS. 12, 13, 14, and 15 are illustrative display structures for adisplay in accordance with an embodiment.

DETAILED DESCRIPTION

A head-mounted device may be provided with a display. The head-mounteddevice may be used in displaying virtual reality content for a user. Toenhance user immersion in the content that is being presented, thedisplay may have a peripheral portion that covers the user's peripheralvision. The peripheral display portion may use individual light-emittingdiodes or other pixels that have a lower density and that displaycontent at a lower resolution than the central portion of the display.Because the user's visual acuity is reduced in the periphery of theuser's visual field, the reduction in the resolution of the peripheraldisplay portion relative to the central portion will not be noticeableto the user. The presence of content in the peripheral display will helpcover all portions of a user's vision and will therefore enhance theimmersive effect of the head-mounted device when the head-mounted deviceis being used to present virtual reality content to the user.

A schematic diagram of an illustrative head-mounted device with aperipheral display is shown in FIG. 1. As shown in FIG. 1, head-mounteddevice 10 may include head-mounted support structures 22. Supportstructures 22 may form glasses, goggles, a helmet, hat, or otherwearable structures that are configured to be mounted (worn) on the headof a user while supporting the components of device 10. Supportstructures 22 may support lenses, display components, and other portionsof device 10.

Device 10 may include control circuitry 12 and input-output devices 16.Control circuitry 12 may include storage and processing circuitry forsupporting the operation of device 10. The storage and processingcircuitry may include storage such as nonvolatile memory (e.g., flashmemory or other electrically-programmable-read-only memory configured toform a solid state drive), volatile memory (e.g., static or dynamicrandom-access-memory), etc. Processing circuitry in control circuitry 12may be used to gather input from sensors and other input devices and maybe used to control display components and other output devices. Theprocessing circuitry may be based on one or more microprocessors,microcontrollers, digital signal processors, baseband processors andother wireless communications circuits, power management units, audiochips, application specific integrated circuits, etc.

To support communications between device 10 and external electronicequipment (e.g., equipment a computer, cellular telephone, or other hostdevice, etc.), control circuitry 12 may include communicationscircuitry. The communications circuitry of control circuitry 12 mayinclude antennas, radio-frequency transceiver circuitry, and otherwireless communications circuitry and/or wired communications circuitry.Circuitry 12, which may sometimes be referred to as control andcommunications circuitry, may, for example, support wirelesscommunications using wireless local area network links, near-fieldcommunications links, cellular telephone links, millimeter wave links,and/or other wireless communications paths.

Input-output devices 16 may be used in gathering user input, ingathering information on the environment surrounding the user, and/or inproviding a user with output. Devices 16 may include sensors 18. Sensors18 may include image sensors, force sensors (e.g., strain gauges,capacitive force sensors, resistive force sensors, etc.), audio sensorssuch as microphones, touch sensors, proximity sensors, optical sensorsthat emit and detect light, ultrasonic sensors, monochromatic and colorambient light sensors, sensors for detecting position, orientation,and/or motion (e.g., accelerometers, magnetic sensors such as compasssensors, gyroscopes, and/or inertial measurement units that contain someor all of these sensors), muscle activity sensors (EMG), radio-frequencysensors (e.g., radar and other ranging and positioning sensors), depthsensors (e.g., structured light sensors and/or depth sensors based onstereo imaging devices), optical sensors such as self-mixing sensors andlight detection and ranging (lidar) sensors that gather time-of-flightmeasurements and/or other measurements to determine distance and/orrelative velocity, humidity sensors, moisture sensors, and/or othersensors.

Sensors 18 may include one or more sensors for monitoring a user'sdirection of gaze. Sensors 18 may, for example, include one or more gazetracking sensors (sometimes referred to as gaze trackers or gazetracking systems). A gaze tracking sensor may, for example, emit one ormore beams of light towards a user's eyes and use an image sensor and/orother light-sensing device to measure light reflections and eye imagesto track the orientation of the user's eyes. Gaze direction informationmay be gathered in real time during operation of device 10 and used inadjusting the content that is displayed for the user.

Input-output devices 16 may also include displays such as display 14.Display 14 may include a central portion such as central display 14C andperipheral portions on the left and right of display 14C such asperipheral portions 14P. In central portion 14C, each eye of a user mayhave a corresponding separate display panel or a single display panelmay be used to provide content to both of a user's eyes. Displays 14Cand 14P may be organic light-emitting diode displays, displays based onarrays of light-emitting diodes formed from crystalline semiconductordies, liquid crystal displays, electrophoretic displays,microelectromechanical systems (MEMs) displays such as displays witharrays of moving mirrors, displays formed from crystalline semiconductorlight-emitting diode dies (e.g., microLEDs), and/or other displays. Withone illustrative arrangement, the central portion of display 14 may beformed using a liquid crystal display or organic light-emitting diodedisplay and the peripheral portion (portions) of display 14 may beformed using a lower resolution array of discrete light-emitting diodes.Other configurations may be used for display 14, if desired.

In addition to display 14, input-output devices 16 may include otherdevices 20. Devices 20 may include components such as status indicatorlights (e.g., light-emitting diodes in devices 10 that serves as powerindicators, and other light-based output devices), speakers and otheraudio output devices, batteries, etc. Devices 20 may also include powertransmitting and/or receiving circuits configured to transmit and/orreceive wired and/or wireless power signals. Devices 20 may includebuttons, rotating buttons, push buttons, joysticks, keys such asalphanumeric keys in a keyboard or keypad, microphones for gatheringvoice commands, touch sensor input devices, touch sensor buttons, touchsensor slider buttons, track pads, and/or other devices for gatheringuser input for controlling the operation of device 10. Devices 20 mayalso include output components such as haptic output devices and otheroutput components.

FIG. 2 is a cross-sectional top view of an illustrative left portion ofa head-mounted device. The right portion of head-mounted device 10 mayhave the same layout. As shown in FIG. 2, head-mounted device 10 mayinclude a central display such as central display 14C that is used inpresenting high resolution images to a user when the user's eyes arelocated in eye boxes such as eye box 32. Central display 14C and theother components of FIG. 2 may be mounted to head-mounted supportstructures 22. A pair of lenses such as lens 26 (e.g., left and rightlenses for the user's left and right eyes) may be respectively alignedwith left and right eye boxes 32 and used to help the user focus ondisplay 14C. Display 14C may be planar or may be curved. Lenses 26 maybe Fresnel lenses or other suitable lenses. Lens holders 28 may be usedto couple lenses 26 to support structures 22. Each lens holder 28 may,for example, have a ring shape that surrounds the periphery or arespective one of lenses 26.

Peripheral display 14P may be located in the user's peripheral vision tothe left and right of central display 14C. For example, the user mayview main display 14C in direction 34 (e.g., a direction that isparallel to the surface normal of display 14C and that is straight aheadof the user) and may view peripheral display 14P in directions such asdirection 36 that are oriented off to the side at a non-zero angle Awith respect to direction 34. The value of A may be for example, atleast 40°, at least 45°, at least 60°, less than 100°, less than 90°, orother suitable value.

Central display 14C may have central pixels 24C (e.g., an array ofcentral pixels). Pixels 24C may display images with a relatively highresolution (e.g., at least 50 pixels per inch, at least 100 pixels perinch, at least 200 pixels per inch, at least 400 pixels per inch, fewerthan 1000 pixels per inch, etc.). Peripheral display 14P may haveperipheral pixels 24P (e.g., an array of peripheral pixels) that arearranged to have a lower density (pixels per unit area) and therefore alower resolution than pixels 24C. Pixels 24P may, for example, have aresolution of 12-25 pixels per inch, at least 5 pixels per inch, atleast 10 pixels per inch, at least 15 pixels per inch, at least 20pixels per inch, fewer than 50 pixels per inch, fewer than 30 pixels perinch, or other suitable resolution. Peripheral display 14P may have aleft portion on the left-hand side of central portion 14C (sometimesreferred to as the left peripheral display of device 10) and a rightportion on the right-hand side of central portion 14C (sometimesreferred to as the right peripheral display of device 10). By using alower pixel density for the left and right peripheral portions ofdisplay 14 relative to the main central portion of display, powerconsumption and the amount of image processing that is required todisplay content for the user can be reduced.

Pixels 24P may be formed using any suitable type of pixel structure(e.g., light-emitting diodes formed from thin-film diodes such asorganic light-emitting diodes, light-emitting diodes formed fromcrystalline semiconductor dies, etc.). Pixels 24C may be formed as partof a display panel such as an organic light-emitting diode displaypanel, a liquid crystal display panel, a display based on a digitalmicromirror device, a liquid-crystal-on-silicon display, or othersuitable display technology. In arrangements in which the brightness oflight-emitting diodes in pixels 24P is relatively high, an optionalneutral density filter such as filter 30 of FIG. 2 may be interposedbetween peripheral display 14P and eye box 32 to help dim display 14P toa comfortable level. Light-emitting diodes in pixels 24P may also bedimmed using pulse-width modulation of the drive currents applied topixels 24P.

To reduce the overall size and weight of device 10 on a user's head,head-mounted support structures 22 may include lightweight materialssuch as polymers. Other materials (e.g., metal, glass, etc.) may also beused in forming head-mounted support structures 22. Head-mounted supportstructures 22 may have a shape that conforms to the generally sphericalshape of a human head. For example, when viewed from above as shown inFIG. 2, peripheral display 14P (and, if desired, some or all of centraldisplay 14C) may have a curved profile that follows the curved outlineof a user's head. Pixels 24P may, for example, be formed on a surfacethat bends about vertical bend axis 38. This surface may form part of acylindrical surface or other curved surface. If desired, pixels 24P maylie on a surface that bends about an axis in the X-Z plane (see, e.g.,pixels 24P of peripheral display 14P of FIG. 3, which are shown ascurving about axis 40, which lies in the X-Z plane). Axis 40 may runparallel to the Y axis or other axis in the X-Z plane (in this example).Moreover, pixels 24P may, if desired, lie on a surface of compoundcurvature (e.g., so that pixels 24P in display portion 14P arerelatively equidistant from a user's eyes).

In general, display portion 14P may have any suitable shape (a shapecurving about a vertical axis such as axis 38 of FIG. 2, a shape curvingaround a horizontal axis such as axis 40 of FIG. 3, a shape having partswith curvature in multiple directions, a shape having planar sectionsthat approximate a curved shape, other three-dimensional shapes, etc.).The shapes of peripheral display 14P that are shown in FIGS. 2 and 3 areillustrative.

To help block lens holder 28 from view, light guiding structures may beused to route light from pixels 24P in front of lens holder 28.Consider, as an example, the arrangement of FIG. 4. In the illustrativeconfiguration of FIG. 4, device 10 has a peripheral display portion 14Pwith pixels 24P that are adjacent to lens holder 28. Lens holder 28 maybe formed from opaque polymer or other material that does not passlight. To help block lens holder 28 from view, light guiding layer 42may be placed in front of lens holder 28. Light guiding layer 42 may,for example, be a coherent fiber bundle layer having multiple parallelfibers 44. The ends of fibers 44 that are adjacent to pixels 24P receivelight from pixels 24P and the opposing ends of fibers 44 providecorresponding output light to eye box 32 for viewing by a user. Fibers44 may be provided with bends and/or the surfaces of layer 42 may havecurved profiles to help guide light into desired location. In theillustrative configuration of FIG. 4, portion 46 of layer 42 overlapslens holder 28 and thereby blocks lens holder 28 from view by a user'seye in eye box 32 (e.g., when the user is viewing display 14 indirection 34). The arrangement of FIG. 4 thereby helps visually hide theinterface (seam) between the innermost edge of peripheral display 14Pand the adjacent outermost edge of central display 14C.

If desired, peripheral display 14P may have pixels that are arrangedwith different densities in different locations. For example, pixels 24Pthat are near to central display 14C such as first pixels R1 may have ahigher resolution (more pixels per inch) than pixels 24P that arefarther from central display 14 such as second pixels R2. The density(number of pixels per unit area) of pixels 14P may vary smoothly andcontinuously or may contain locations in which pixel density variesdiscontinuously. As one example, pixels 14P in region R1 of peripheraldisplay 14P may have a first density and pixels 14P in region R2 ofperipheral display 14 may have a second density that is lower than thefirst density.

Arrangements in which pixels 14P exhibit a continuously decreasingdensity at increasing distances from the edge of central display 14C,arrangements in which pixels 14P have a constant density throughoutdisplay 14P, or other pixel density arrangements may also be used. Ifdesired, density gradient effects can be implemented by renderingcontent on the portion of display 14P that is closest to display 14Cwith a higher resolution than content on the portion of display 14P thatis farthest from display 14C (e.g., even in arrangements in whichdisplay 14P has pixels 24P of constant density). Rendering-basedresolution gradients such as these may also be used in peripheraldisplays with pixel density gradients.

If desired, lens holder 28 may be formed from a light-diffusingmaterial, as shown in FIG. 5. Lens holder 28 of FIG. 5 may, for example,be formed from polymer with embedded light-scattering particles. Thelight-scattering particles may be formed from inorganic material such astitanium oxide or other metal oxide that has a different (e.g., higher)refractive index than the polymer in which the light-scatteringparticles is embedded. The polymer and light-scattering particles may betransparent to visible light. Lens holder 28 in this type of arrangementmay overlap pixels 24P along the edge of peripheral display 14P as shownin FIG. 5. During operation, light emitted by the overlapped pixels 24Pin display 14P is diffused when passing through the light diffuserformed from lens holder 28. This diffusing arrangement helps visuallyobscure the interface (seam) between peripheral display 14P and centraldisplay 14C (e.g., when a viewer is viewing display 14 in direction 34).

In the illustrative configuration of FIG. 6, a separate diffuser (lightdiffuser 48) overlaps pixels 24P along the edge of display 14P to helpvisually obscure the interface between peripheral display 14P andcentral display 14C (e.g., when a viewer is viewing display 14 indirection 34). Pixels 24P may be formed adjacent to lens holder 28 orsome of pixels 24P may be interposed between lens holder 28 and diffuser48 (e.g., so that some of pixels 24P overlap lens holder 28). Lightdiffuser 48 may be formed from clear polymer with embeddedlight-scattering particles. Light diffuser 48 may be provided in theform of a sheet of light diffuser material, as a coating on a portion ofdisplay 14P, as a molded polymer member, and/or as any other suitablelight diffuser structure. Combinations of the arrangements shown inFIGS. 4, 5, and/or 6 may also be used to help cover the interfacebetween peripheral display 14P and central display 14C, if desired.

The interface between display 14C and peripheral display 14P may be madeless noticeable by matching the brightness (luminance) and color (e.g.,color coordinates) of the content being displayed on peripheral display14P to the content being displayed on display 14C (or at least thecontent being displayed on the left and right edges of display 14C). If,for example, display 14C or a strip of pixels along an edge of display14C is displaying dim orange content, display 14P may be adjusted todisplay matching dim orange content. This approach helps make the imageon display 14 appear seamless and continuous.

The content of displays 14P and 14C may not be located at equal opticaldistances from eye boxes 34, which gives rise to a potential forparallax effects as a user's eyes move and point in differentdirections. For example, content on main display 14C may be presented ina focal plane that is far from the user (e.g., a distance of about 20 cmto infinity), whereas content on peripheral display 14P, which is notgenerally affected by an intervening lens such as lens 26, has a muchsmaller optical distance (e.g., a few centimeters). Display 14Ptherefore displays content at an optical distance that is less than thecontent displayed on display 14C. This can result in a parallax-inducedmismatch between content on displays 14P and 14C.

A side view of an illustrative eye is shown in FIG. 7. As shown in FIG.7, a user's eye may point in different directions at different times.For example, eye 50 may point horizontally (user gaze direction b), maypoint upwards (user gaze direction a), or may point downwards (user gazedirection c). Different gaze directions (e.g., gaze directions withdifferent elevation angles as shown in the example of FIG. 7 and/or gazedirections with different azimuth angles) can lead to parallax due tothe different optical distances of displays 14P and 14C. During use ofdevice 10, display content on display 14 may be adjusted dynamically sothat movement of the user's eye (e.g., movement from a first orientationin which the user is viewing display 14 in gaze direction a to a secondorientation in which the user is viewing display 14 in gaze direction c)does not cause undesired visual artifacts on display 14.

Consider, as an example, illustrative content such as horizontal line 52that is being displayed on display 14 of FIG. 8. When the user isviewing display 14 with gaze direction b, parallax will not be presentand line 52 on central display 14C will appear continuous across all ofdisplay 14. In particular, peripheral portion 52 b of line 52 onperipheral display 14P will be correctly aligned with line 52 on centraldisplay 14C.

If, however, the user gazes downward, parallax effects will causeperipheral line portion 52 c on peripheral display 14P to appear offsetupwards with respect to line 52 on central display 14. Similarly, if theuser gazes upwards, parallax effects will cause peripheral line portion52 a on peripheral display 14P to appear offset downwards with respectto line 52.

A flow chart of illustrative operations that may be used by controlcircuitry 12 of device 10 to compensate for these parallax effects andthereby ensure that display 14 presents content to the user withoutundesired visual artifacts is shown in FIG. 9.

During the operations of block 60, the gaze tracker (gaze trackingsensor) in sensors 18 is used by control circuitry 12 to gatherinformation on the direction of gaze of the user's eyes.

During the operations of block 62, control circuitry 12 may presentcontent on display 14 that has been adjusted based on the measured gazedirection to correct for parallax effects due to the different effectivedistances of the content on displays 14C and 14P from eye boxes 32. Theoperations of blocks 60 and 62 may be performed continually during useof device 10, as illustrated by line 64.

With one illustrative arrangement, control circuitry 12 over-renders theedges of the central content for display 14 during block 62. This edgecontent is displayed on display 14P adjacent to central display 14.While displaying the edge content on display 14P, the edge content isdynamically shifted up or down on display 14P based on the measured gazedirection of the user. The content on central display 14C is leftunaltered. Consider, as an example, a scenario in which the user islooking in gaze direction c. In response to measuring that the user'sdirection of gaze is gaze direction c, control circuitry 12 shifts theedge content on display 14P downward relative to the content on display14C (e.g., to align line portion 52 c with line 52 on central portion14C). Horizontal (azimuthal) parallax-induced mismatch may also becorrected in this way.

With another illustrative arrangement, control circuitry 12 stretches(warps) image content on peripheral display 14P to reduceparallax-induced mismatch between the content on display 14P and display14C during the operations of block 62. For example, the portion ofcontent on display 14P at which the user is looking (e.g., portion ofthe image closest to the eye's fixation point) may be shifted while therest of the peripheral image is warped to make up for mismatch elsewherein the image.

Another illustrative approach involves rendering content for peripheralportion 14P during block 62 so that the center of projection of thecontent on peripheral display 14P is coincident with the physicalposition of the user's pupil. This approach also compensates fordifferences in optical distance between peripheral display 14P andcentral display 14C.

The content on peripheral display 14P may include moving objects, solidcolors, and/or other content. If desired, the content that is to bedisplayed on peripheral display 14P may be obtained by smearing out edgecontent from display 14C onto display 14P. This type of arrangement isshown in FIG. 10. As shown in FIG. 10, display 14 includes centraldisplay 14C and flanking lower-resolution display areas (peripheraldisplay 14P). During operation of device 10, control circuitry 12 canrender content corresponding to width W of display 14. The middle ofthis content may be displayed on central display 14C. The outermost leftand right edges 66 of this content area may extend off the edges ofcentral display 14C onto peripheral display 14P. To cover all of thesurface area of peripheral display 14P, the content in edge portions 66may be stretched laterally to cover all of peripheral display 14P ratherthan being confined to strip-shaped edge areas 66. If desired, parallaxcorrection operations of the type described in connection with FIG. 9can be performed on the content that is stretched out to cover display14P to avoid parallax-induced mismatch between the stretched-out contentand the content on display 14C.

If desired, the content on peripheral display 14P may be obtained fromthe content on display 14C using other approaches. As an example, theluminance and color of the content on peripheral display 14P may bedetermined from the average luminance and color of the content oncentral display 14C or may be determined from the average luminance andcolor of left and right edge portions of the content on central display14C. Solid regions of color (e.g., solid regions with matching luminanceand color), color gradients (e.g., color that fades to black or thatreduces in saturation as the distance from display 14C increases), bandsof color, and/or other patterns of peripheral content may be provided tofill peripheral display 14P. Display driver circuitry in display 14(e.g., a timing controller integrated circuit(s)) may be shared betweendisplays 14C and 14P. Configurations in which peripheral display 14P isdriven separately from main display 14C and/or in which the content ondisplay 14P is provided in a separate content stream may be used, ifdesired.

Although a user's peripheral vision has a lower spatial resolution thanthe center of the user's visual field, peripheral vision can besensitive to light and motion. Accordingly, if an object is movingacross the user's field of view, that object will be perceived on aperipheral display area before the object enters central display 14C.The inclusion of peripheral display 14P may therefore help provide auser with advance notice of objects entering the user's main field ofview. The inclusion of content in peripheral display 14P can also avoidundesired tunnel vision effects in which a user perceives that thecontent on central display 14C (e.g., non-black content) is floatingwithin an extended black region.

To conserve power while operating display 14, unused pixels (e.g.,unused pixels 24P in peripheral display 14) can be turned off whenappropriate. For example, control circuitry 12 can use the gaze trackingsystem in sensors 18 to monitor the user's direction of gaze. When theuser's gaze is directed more than a threshold amount (e.g., more than athreshold angle) away from the center of display 14, some of theperipheral pixels in display 14 will become unviewable by the user. Asshown in the illustrative top view of device 10 of FIG. 11, for example,a user's gaze may be directed in direction 70 to the right of display14. When the user's direction of gaze is angled to the right in thisway, pixels 24P in the left-hand portion of peripheral display 14P willbe unviewable to the user. Because the left-hand pixels 24P areinvisible to the user (in this example), these pixels may be temporarilypowered down (e.g., these pixels may be turned off) to conserve power.Right hand pixels 24P can similarly be powered down to conserve power inresponse to determining that the user's direction of gaze is orientedtowards the left of display 14 (e.g., a direction in which theright-hand pixels 24P are not visible in the user's peripheral vision).All of the peripheral pixels 24P on the unviewable side of display 14 orjust the outermost (least viewable) peripheral pixels 24P may be powereddown. Configurations in which power consumption is reduced bymomentarily reducing pixel output luminance without fully turning offpixels 24P may also be used.

Illustrative configurations for forming pixels in display 14 are shownin FIGS. 12, 13, 14, and 15.

Pixels 24C in central portion 12C may be organic light-emitting diodepixels, pixels with light-emitting diodes formed from crystallinesemiconductor dies, liquid crystal display pixels (e.g., backlitpixels), microelectromechanical systems (MEMs) display pixels such asdigital micromirror pixels, liquid-crystal-on silicon pixels, or othersuitable pixels. In the illustrative configuration of FIG. 13, pixels24C in central display 14C are formed on a substrate such as a flexibledisplay substrate (e.g., an organic light-emitting diode displaysubstrate). Pixels 24P in the example of FIG. 12 are formed onperipheral edge portions of the same flexible display substrate aspixels 24C. Pixels 24P may be, for example, organic light-emitting diodepixels formed from the same thin-film circuitry used in forming pixels24C.

As shown in FIG. 13, pixels 24P may be formed on a flexible substratelayer 76. Substrate layer 76 may be, for example, a flexible sheet ofpolyimide or other flexible layer of polymer. If desired, substrate 76may be formed from an elastomeric substrate material (e.g., silicone).Pixels 24P may be crystalline semiconductor dies forming respectivelight-emitting diodes. Substrate layer 76 may have a mesh shape (e.g., ashape with islands interconnected by stretchable serpentine segments) ormay have other stretchable shapes. For example, substrate layer 76 mayhave fingers 80. Fingers 80 may be formed from elongated protrusions ofsubstrate layer 76 that are separated by interposed slots 78. theelongated shapes of fingers 80 may allow fingers 80 to be mounted on athree-dimensional surface on the inside of support structure 22 (see,e.g., support structure 22 of FIG. 2). This surface may, for example,have a curved profile, may be a surface of compound curvature, etc.

FIG. 14 shows how central display 14C and/or peripheral display 14P maybe formed from rigid display panels (e.g., planar panels). Display 14Cmay be, for example, a flexible display or a rigid display formed from arigid substrate. Display 14P may be, for example, a printed circuitboard (e.g., a rigid printed circuit board formed from a rigid printedcircuit board material such as fiberglass-filled epoxy) on whichindividual light-emitting diodes for pixels 24P have been mounted.

FIG. 15 shows how pixels 24P in peripheral portion 14P may be mounted ona molded polymer support structure or other support structure with acurved inner surface profile (support structure 86). Structure 86 maybe, for example, a molded polymer support having an inner surface ofcompound curvature with patterned metal traces whereas pixels 24P onstructure 86 may be microLEDs or other light-emitting diodes formed fromcrystalline semiconductor dies that are soldered to the metal traces.

The foregoing is merely illustrative and various modifications can bemade to the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. An electronic device, comprising: ahead-mountable support structure; lenses supported by the head-mountablesupport structure; a display supported by the head-mountable supportstructure that has a central portion and a peripheral portion, whereinthe central portion is configured to display central content that isviewable through the lenses from eye boxes and wherein the peripheralportion is configured to display peripheral content that is viewablefrom the eye boxes without viewing through the lenses; a gaze trackingsystem configured to monitor the eye boxes to gather gaze directioninformation; and control circuitry configured to adjust the peripheralcontent based on the gaze direction information.
 2. The electronicdevice defined in claim 1 wherein the central portion has central pixelsof a first density and wherein the peripheral portion has peripheralpixels of a second density that is lower than the first density.
 3. Theelectronic device defined in claim 2 wherein the peripheral pixels areon a surface having compound surface curvature.
 4. The electronic devicedefined in claim 2 wherein the peripheral pixels are formed on aflexible substrate having substrate portions separated by gaps.
 5. Theelectronic device defined in claim 2 wherein the control circuitry isconfigured to adjust the peripheral content to correct forparallax-induced mismatch between the peripheral content and the centralcontent.
 6. The electronic device defined in claim 5 wherein the controlcircuitry is configured to adjust the peripheral content to correct forthe parallax-induced mismatch by shifting the peripheral contentrelative to the central content based on the gaze direction information.7. The electronic device defined in claim 5 wherein the controlcircuitry is configured to adjust the peripheral content to correct forthe parallax-induced mismatch by warping the peripheral content relativeto the central content based on the gaze direction information.
 8. Theelectronic device defined in claim 5 wherein the control circuitry isconfigured to adjust the peripheral content to correct for theparallax-induced mismatch by rendering the peripheral content with acenter of projection that is coincident with a physical pupil location.9. The electronic device defined in claim 2 wherein the controlcircuitry is configured to selectively depower at least some of theperipheral pixels based on the gaze direction information.
 10. Theelectronic device defined in claim 2 wherein the control circuitry isconfigured to produce the peripheral content from stretchedover-rendered edge portions of the central content.
 11. The electronicdevice defined in claim 2 wherein the control circuitry is configured toadjust the peripheral content to have a color and luminance that ismatched to a portion of the central content.
 12. An electronic device,comprising: a head-mountable support structure; left and right lensessupported by the head-mountable support structure and aligned withrespective left and right eye boxes; a display supported by thehead-mountable support structure that has a central portion and aperipheral portion, wherein the central portion is operable to displaycentral content that is viewable through the left and right lenses fromthe left and right eye boxes, respectively, wherein the peripheralportion is operable to display peripheral content that is viewable fromthe left and right eye boxes without viewing through the lenses, andwherein the peripheral portion has a left peripheral portion along aleft edge of the central portion and a right peripheral portion along aright edge of the central portion; a gaze tracking system operable tomonitor the left and right eye boxes to gather gaze directioninformation; and control circuitry operable to adjust the peripheralcontent based on the gaze direction information.
 13. The electronicdevice defined in claim 12 wherein the central portion has centralpixels of a first density, wherein the peripheral portion has peripheralpixels of a lower density than the central portion, and wherein thecontrol circuitry is operable to adjust the peripheral content based onthe gaze direction information to reduce parallax-induced mismatchbetween the peripheral content and the central content.
 14. Theelectronic device defined in claim 12 further comprising light-diffusinglens holders for the left and right lenses, wherein light from someperipheral pixels in the peripheral portion passes through thelight-diffusing lens holders.
 15. The electronic device defined in claim12 further comprising a neutral density filter that is betweenperipheral pixels in the peripheral portion and the left and right eyeboxes.
 16. The electronic device defined in claim 12 further comprisinga light diffuser that overlaps at least some peripheral pixels in theperipheral portion.
 17. An electronic device, comprising: ahead-mountable support structure; a lens supported by the head-mountablesupport structure and aligned with an eye box; a display supported bythe head-mountable support structure that has a central portion viewablefrom the eye box through the lens and a peripheral portion viewable fromthe eye box without viewing through the lens, wherein the centralportion has central pixels of a first density and wherein the peripheralportion has peripheral pixels of a second density that is less than thefirst density; a gaze tracking system configured to monitor the eye boxto gather gaze direction information; and control circuitry configuredto adjust the peripheral portion based on the gaze directioninformation.
 18. The electronic device defined in claim 17 wherein theperipheral pixels comprise crystalline semiconductor light-emittingdiode dies.
 19. The electronic device defined in claim 18 wherein theperipheral pixels have a resolution of at least 10 pixels per inch andless than 50 pixels per inch.
 20. The electronic device defined in claim17 wherein the control circuitry is configured to depower some of theperipheral pixels in response to determining from the gaze directioninformation that those peripheral pixels are unviewable from the eyebox.
 21. An electronic device, comprising: a head-mounted supportstructure; a lens supported by the head-mounted support structure andaligned with an eye box; and a display supported by the head-mountedsupport structure that has a central portion viewable from the eye boxthrough the lens and a peripheral portion viewable from the eye boxwithout viewing through the lens.
 22. The electronic device defined inclaim 21 wherein the central portion has central pixels of a firstdensity and wherein the peripheral portion has peripheral pixels of asecond density that is less than the first density.
 23. The electronicdevice defined in claim 21 further comprising: control circuitryconfigured to adjust peripheral content displayed on the peripheralportion to correct for parallax-induced mismatch between the peripheralcontent and central content displayed on the central portion.